cc: Avoid expensive RenderingStats collection.

cc/picture.cc

Index: cc/picture.cc
diff --git a/cc/picture.cc b/cc/picture.cc
index c850fd8e3e954c7f75068a7e383c557c1dbf092b..35a935dd0264c4619aad5370886e664b6c70505b 100644
--- a/cc/picture.cc
+++ b/cc/picture.cc
@@ -50,7 +50,7 @@ scoped_refptr<Picture> Picture::Clone() const {
 }
 
 void Picture::Record(ContentLayerClient* painter,
-                     RenderingStats& stats) {
+                     RenderingStats* stats) {
   TRACE_EVENT2("cc", "Picture::Record",
                "width", layer_rect_.width(), "height", layer_rect_.height());
 
@@ -80,11 +80,15 @@ void Picture::Record(ContentLayerClient* painter,
   canvas->drawRect(layer_skrect, paint);
 
   gfx::RectF opaque_layer_rect;
-  base::TimeTicks beginPaintTime = base::TimeTicks::Now();
+  base::TimeTicks begin_paint_time;
+  if (stats)
+    begin_paint_time = base::TimeTicks::Now();
   painter->paintContents(canvas, layer_rect_, opaque_layer_rect);
-  stats.totalPaintTime += base::TimeTicks::Now() - beginPaintTime;
-  stats.totalPixelsPainted += layer_rect_.width() *
-                              layer_rect_.height();
+  if (stats) {
+    stats->totalPaintTime += base::TimeTicks::Now() - begin_paint_time;
+    stats->totalPixelsPainted +=
+        layer_rect_.width() * layer_rect_.height();
+  }
 
   canvas->restore();
   picture_->endRecording();